This invention relates to an electronic musical instrument, and more particularly to an improvement of an electronic musical instrument embodying to a system in which a tone pitch, a tone color and volume of a musical tone controlled by the use of voltage control type circuits.
In general, in an electronic musical instrument called a music synthesizer, voltages corresponding to the tone pitches of respective keys (hereinafter referred to as "tone pitch voltages" when applicable) are produced in response to the depression of the keys, thereby controlling the operation of a voltage control type oscillator to produce tone signals having frequencies corresponding to the tone pitches of the depressed keys. The tone pitch voltages corresponding to the keys are set by a resistance type voltage division circuit or the like. However, the tone pitch voltages are fixedly set in accordance with a predetermined temperament, for instance an equal temperament, and therefore it is impossible to obtain musical scales other than those conforming to the predetermined temperament.
In order to overcome this difficulty, an electronic musical instrument has been proposed in the U.S. patent application Ser. No. 770,718 filed on Feb. 22, 1977 and assigned to the same assignee as the present application. In this electronic musical instrument, control voltages corresponding to the keys or the octave range of the keys (hereinafter referred to as "key corresponding control voltages" when applicable) are produced in addition to the aforementioned tone pitch voltages, and the sums of the tone pitch voltages and the key corresponding control voltages, or voltages obtained by mixing these two kinds of voltages are employed to control the oscillation frequencies of a voltage control type oscillator thereby to obtain scales according to temperaments other than the temperament predetermined by the tone pitch voltages. In addition the key corresponding control voltages are employed to control various tonal elements such as tone pitches, tone colors, and volumes thereby to improve the effects in performance. However, in this electronic musical instrument since positive and negative voltages are required to be produced by a circuit for generating the key corresponding control voltages a resistance type voltage division circuit for providing positive voltages and a resistance type voltage division circuit for providing negative voltages should be provided in the control voltage generating circuit, as a result of which the circuitry of the electronic musical instrument is rather intricate.